Sheet guide and cooling apparatus

ABSTRACT

A sheet guide and cooling apparatus for preventing curl in sheets bearing a developed image, the image being permanently fixed to the sheet by application of heat and pressure. The apparatus is positioned to have a flat thermally conductive surface establishing a path for the sheet, downstream of the fixing area, the path extending in a plane substantially coplanar with the plane of sheet travel in the fixing station. Vacuum means associated with the surface maintains successive incremental portions of a sheet in face-to-face contact with the flat surface as it is being guided for at least a predetermined period as the sheet moves along the path and furthermore, provides a flow of cooling air for the surface.

United States Patent Wurl Oct. 21, 1975 [54] SHEET GUIDE AND COOLING APPARATUS 3,810,735 5/1974 Moser 432/59 1 Inventor: Donald spencerport, 31233138? 111333 E'fifilfifflfifi.iiiiiii i:::::: 225%? 73 Assignee; Eastman Kodak Company, 3,861,863 1/1975 Kudi 432/228 Rochester, NY. h C b Primary ExaminerJo n J. am [22] Filed: 1974 Assistant Examiner-Henry C'Yu n [21] A l N 438,829 Attorney, Agent, or Firm-L. P. Kessler 52 US. Cl. 432/59; 432/228; 34/66; [57] ABSTRACT 34/92 A sheet guide and cooling apparatus for preventing [51] Int. Cl. F27B 9/28; F26B 19/00 curl in heets bearing a developed image the image [58] Field Of Search 432/59-62, being permanentlyfixed to the heet by application of 432/2 heat and pressure. The apparatus is positioned to have 95, 155, 162, 66 a flat thermally conductive surface establishing a path for the sheet, downstream of the fixing area, the path References Cited extending in a plane substantially coplanar with the UNITED STATES PATENTS plane of sheet travel in the fixing station. Vacuum 3,316,655 5,1967 Bocciardo 34/92 means associated with the surface maintains succes- 3,402,762 9/1968 Kreutteretal. 34/66 Sive incremental Portions of a Sheet in face-to-face 3,435,751 4/1969 Goodman et a]. 34/162 Contact with the flat surface as it is being guided for at 3,447,247 6/1969 Daane 34/122 least a predetermined period as the sheet moves along 3,449,54 1969 Adamek et al. 219/216 the path and furthermore, provides a flow of cooling 3,515,855 6/1970 Mix, Jr 432/59 air f the f 3,517,164 6/1970 Huggins et aL. 432/59 3,659,348 5/ 1972 Frank 34/ 162 3 Claims, 2 Drawing Figures SHEET GUIDE AND COOLING APPARATUS BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to sheet handling and in particular to an apparatus for preventing curl in sheets subject to processing by application of heat and pressure.

2. Description of the Prior Art In electrophotographic reproduction techniques, a developed image formed by electrostatic attraction of toner particles to a latent image charge pattern on a photoconductive surface is transferred to a receiver sheet to form a copy of an original. The toner particles are permanently fixed to the receiver sheet by the concomitant application of heat and pressure in the proper combination to melt and fuse the particles to the sheet. Control of the fixing parameters is critical in that heat and pressure have a deleterious effect on the receiver sheet material. Elevated temperatures tend to cause evaporation of moisture normally present in the sheet, thus lowering the moisture content of the sheet material. The lower moisture content causes the sheet to become brittle, as well as inducing warping or curl therein. Application of pressure to the sheets accentuates the tendency of the material to warp or curl.

SUMMARY OF THE INVENTION It is therefore a primary object of this invention to provide an apparatus for handling sheets processed by application of heat and pressure in such a way so as to prevent curl from occurring therein.

It is another object of this invention to maintain sheets processed by application of heat and pressure in a flat condition for a period of time after processing to prevent curl.

It is still another object of this invention to cool the sheets processed by application of heat and pressure while the sheets are maintained in a flat condition to further provide for curl prevention.

Accordingly, there is herein provided a guide apparatus for sheets processed by heat and pressure, the apparatus having a thermally conductive flat surface for establishing, downstream of the processing station, a sheet travel path, the path being substantially complanar with the plane of sheet travel in the processing station. Vacuum means, cooperating with the flat surface, maintains successive incremental portions of a sheet being guided in face-to-face contact with the surface for at least a predetermined period as the sheet moves along the path and, furthermore, provides a flow of cooling air for the surface.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view, in section, of the sheet guide and cooling apparatus according to this invention showing its relation to an exemplary processing station; and

FIG. 2 is a transverse sectional view of the apparatus of this invention taken along lines 2--2 of FIG- 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, FIG. 1 shows a sheet guide and cooling apparatus located immediately adjacent a sheet travel path P along with a sheet S having a developed image D thereon is transported. In the embodiment shown, the sheet S is an electrophotographically produced copy sheet and the developed image D is comprised of charge-attracted toner particles. The apparatus 10 maintains the sheet S in a flat condition and provides for the cooling thereof, as described hereinbelow, as the sheet travels between a heat and pressure applying processing station, such as an image fixing apparatus 12, and an exit transport mechanism 14.

In the particular arrangement shown, the image fixing apparatus 12 is a fuser assembly having a pressure roller 16 and a heated fuser roller 18 mounted on opposite sides of the sheet travel path P for melting the particles which comprise the image D and fusing them with the sheet S. The rollers are relatively adjustable so as to apply both heat and pressure in controlled proportions to a sheet S passing therebetween in order to permanently fix the image to the sheet. The pressure to which the sheet S is subjected is regulated by a pressure controlling device 20 acting on the bearing (not shown) supporting the fuser roller 18. The pressure regulating apparatus 20 is mounted in a C-shaped support 22 which is hinged for movement on the bearing (not shown) supporting the pressure roller 16. A gear 24 controls the angular position of the support 22 by its interaction with a rack 26 on the support 22. In the position shown in FIG. 1, the fuser roller 18 and pressure roller 16 are maintained in their pressure applying position. If it is desired to release the pressure between the rollers, the support 22 is moved clockwise by the counterclockwise rotation of the gear 24 thus permitting the fuser roller 18 to move vertically downward in the guide blocks 28 to relieve the pressure between the two rollers. The structure of the fixing apparatus 12, which forms no part of this invention, is more fully described in Research Disclosure Bulletin of Aug. 1973, No. 112 (pages 39, 40).

The exit mechanism 14, which may be of any particular construction, is shown in this arrangement as being comprised of a set of transport rollers 30 which direct copy sheets selectively into either a first exit channel 32 or a second exit channel 32'. The channel 32 is a continuation of the paper path P while the second exit channel 32' is at an angle thereto and constitutes a secondary path P. Selection of the desired path of travel for the respective sheets is obtained by a pivotable diverter 34, the position of which is controlled by an actuator 36. When in the position shown in full lines of FIG. 1, the diverter 34 permits a sheet S to enter the exit channel 32 maintaining its travel along the path P. If it is desired to guide the sheet into the channel 32', the diverter 34 is moved to its position shown in broken lines so as to intercept the path P in order that the sheet will be redirected along the path P.

The sheet guide and cooling apparatus 10 has a thermally conductive flat guideplate 38 located immediately above the path P, the guideplate extending over a substantial portion of the path between the nips of the fixer assembly 12 and the exit assembly 14. As is apparent from FIG. 1, the path P is a straight line path from the fixer assembly 12 and the exit assembly 14 and the plane of the path established by the guideplate 38 is substantially coplanar with the plane of the path through the fixer assembly. The location of the guideplate 38 above the path P is preferable to prevent smearing of the toner particles (located on the underside of sheet S) when in their melted condition. The

guideplate 38 has a plurality of openings 40 extending therethrough and a series of heat transfer fins 42 extending outwardly from the guideplate on the opposite side of the plate from the path P. A housing 44 for directing cooling air to the heat transfer fins 42 is formed, in part, by a plurality of concave sidewalls 46 interconnected with the guideplate 38, approximating the shape of the rollers so as to enable the housing to extend as close as possible to the respective roller nips. End walls 48 and a top wall 50 are interconnected with the remaining structure so as to form the completed housing 44.

Mounted on the housing 44 is a chamber 52 which communicates with the intake of a vacuum blower 54 (FIG. 2). The chamber 52 has a first opening 56 communicating with a first opening 58 in the top wall 50 of the housing 44. Spaced from the first opening 56 is a second opening 60. The opening 60 communicates with a second opening62 in the top wall 50 of the housing 44. The flow continuity of the chamber 52 is interrupted by a plug 64 located between the first opening 56 and the second opening 60. In this manner, air drawn into the chamber 52 by the vacuum blower 54 through an open end 66 of the chamber will be forced to flow through the cooperating first openings 56 and 58 into the housing 44 and thence back into the chamber 52 through the cooperating second openings 62 and 60. The vacuum blower 54 is selected so as to establish a flow of air in the housing 44 and a pressure condition therein somewhat below atmospheric pressure. Therefore, a sheet traveling along the path P will be drawn into contact with the guideplate 38 due to the establishment of the subatmospheric condition communicated to the area of the path P by means of the openings 40 in the plate 38 and, as a result, the sheet will have successive incremental portions positively maintained in face-to-face contact with the guideplate to retain the sheet in a flat orientation in order to reduce any tendency for the sheet to curl. It is, of course, understood that if the path P (and the resulting plane of the sheet) describes asurface which is curvilinear in the direction transverse to the path, the guideplate 38 will be of a similar configuration in the transverse direction to maintain a uniform shape for the planes of the sheet over the entire travel path so as to prevent sheet curl.

While the sheet S is in contact with the guideplate 38 in its travel from the nip of the fixer arrangement 12 to the nip of the exit arrangement 14, the heat transferred to the sheet during the fixing process will in turn be transferred through the thermally conductive plate to the fins 42. The flow of air across the fins 42 under the influence of the vacuum blower 54 will serve to remove the heat from the area of the fins 42 to more efficiently cool the sheet as it travels along the path P. The length of the guideplate 38 is selected so that the sheet will be maintained in contact with the guideplate for a predetermined period. The period is such that the heat imparted to the sheet will be substantially dissipated. In the preferred embodiment, the sheets travel along the path P at a speed of approximately ll in/sec and the,

length of the guideplate 38 is approximately 5 inches. This has proven sufficient to permit the removal of enough heat to prevent the tendency of the sheet to curl.

From the foregoing it is apparent that there is herein provided a sheet guide and cooling apparatus capable of preventing curl in sheets processed by application of heat and pressure. The invention has been described in detail with particular reference to a preferred embodiment thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scope of the invention as claimed.

I claim:

1. In an apparatus for processing a sheet bearing a developed image, said apparatus having a fixing station guide means defining a thermally conductive sheet guide surface parallel to and closely adjacent said given plane downstream of said fixing station, said guide means including an elongated guideplate a series of openings extending therethrough, said guideplate having at least one thermally conductive fin extending therefrom to facilitate cooling of said sheet, said fin being located out of said sheet travel,

, path; and

means for positively maintaining successive incremental portions of sheets traveling in said path in face-to-face contact with said sheet guide surface for at least a predetermined period as such sheets move along said path.

2. The invention of claim 1, wherein said sheet guide further comprises a housing surrounding said thermally conductive fins and wherein said means for maintaining successive incremental portions of said sheets in face-, to-face contact with said sheet guide surface includes.

vacuum means communicating with said housing to establish a partial vacuum therein.

3. The invention of claim 2, whereinsaid vacuum means includes a conduit open at one end, a vacuum blower connected to said conduit at the other end thereof, a plurality of intercommunicating passages between said conduit and said housing, and meansfor directing a continuous flow of cooling air at subatmospheric pressure induced by said vacuum blower past 1 said guide surface. 

1. In an apparatus for processing a sheet bearing a developed image, said apparatus having a fixing station for receiving the sheets and rendering said developed image permanently fixed to the sheet by application of heat and pressure, means for establishing a sheet travel path downstream of said fixing station, said path extending in a given plane substantially coplanar with the plane of sheet travel in said fixing station, said means comprising: guide means defining a thermally conductive sheet guide surface parallel to and closely adjacent said given plane downstream of said fixing station, said guide means including an elongated guideplate a series of openings extending therethrough, said guideplate having at least one thermally conductive fin extending therefrom to facilitate cooling of said sheet, said fin being located out of said sheet travel path; and means for positively maintaining successive incremental portions of sheets traveling in said path in face-to-face contact with said sheet guide surface for at least a predetermined period as such sheets move along said path.
 2. The invention of claim 1, wherein said sheet guide further comprises a housing surrounding said thermally conductive fins and wherein said means for maintaining successive incremental portions of said sheets in face-to-face contact with said sheet guide surface includes vacuum means communicating with said housing to establish a partial vacuum therein.
 3. The invention of claim 2, wherein said vacuum means includes a conduit open at one end, a vacuum blower connected to said conduit at the other end thereof, a plurality of intercommunicating passages between said conduit and said housing, and means for directing a continuous flow of cooling air at subatmospheric pressure induced by said vacuum blower past said guide surface. 